A liquid crystal display device for use in an in-vehicle display device has recently attracted an attention. Such an in-vehicle liquid crystal display device is demanded that a moving image display performance be secured even at a low temperature (an ultracold temperature) in a range of approximately −30° C. to −20° C. However, a liquid crystal responds slowly at such an ultracold temperature, thereby causing a problem that a moving image display quality, in particular, is deteriorated.
Overdrive (a gray scale transition emphasis process) is known as a technique for quickening a response time of the liquid crystal. According to the overdrive, (i) a gray scale of higher than a current input gray scale is outputted in a case where the current input gray scale is higher than a previous input gray scale or (ii) a gray scale of lower than a current input gray scale is outputted in a case where the current input gray scale is lower than a previous input gray scale, so that the response time of liquid crystal is quickened. Patent Document 1 discloses a technique for carrying out overdrive (forecasting type overdrive) in accordance with (i) a gray scale that is forecasted to reach by a previous response and (ii) a current input gray scale.
Note however that, in a VA mode, (e.g., in an MVA liquid crystal panel), a pixel includes regions in which response times of the liquid crystal are different from each other (see Patent Document 2). This can cause an abnormal response (hereinafter, referred to as an angular response) when overdrive (e.g., the forecasting overdrive) is carried out, in which abnormal response a response waveform rises first and then falls rapidly. Specifically, in a case where a first gray scale (a low gray scale) and a second gray scale (a middle or high gray scale) are inputted, and the second gray scale is subsequently kept to be inputted, then a waveform rises once to the second gray scale from the first gray scale, due to a region in the pixel where the liquid crystal quickly responds, in response to overdrive which is carried out based on a gray scale transition from the first gray scale to the second gray scale. However, after the overdrive is finished, the response waveform remarkably falls from the second gray scale, due to a region in the pixel where the liquid crystal slowly responds. This causes an angular response.
The angular response becomes noticeable particularly at a low temperature at which a viscosity of the liquid crystal is increased. Thus, a liquid crystal display device (e.g., an in-vehicle liquid crystal display device), in which it is required to carry out a moving image display even at a low temperature, causes the following problem. That is, even if the gray scale transition emphasis process is carried out so as to quicken a response time of the liquid crystal at the low temperature, improvement in the display quality cannot be obtained due to the generation of the angular response.
(Patent Document 1)    Japanese Unexamined Patent Application Publication, Tokukai, No. 2004-246312 (published on Sep. 2, 2004)
(Patent Document 2)    Japanese Unexamined Patent Application Publication, Tokukai, No. 2004-302460 (published on Oct. 28, 2004)